<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
</head>
<style>
    body {
        background-color: black;
    }

    .wrap {
        display: flex;
        width: 100%;
    }

    #rectangle1 {
        width: 60px;
        height: 60px;
        background: linear-gradient(225deg, transparent 43px, #4facfe 43px, #00f2fe 100%);
        border-radius: 30px 0 0 30px;
        animation: rectangle1Run 5s ease infinite;
    }

    #rectangle2 {
        width: 100%;
        flex: 1;
        height: 60px;
        background: linear-gradient(45deg, transparent 43px, #f5576c 43px, #f093fb 100%);
        margin-left: -50px;
        border-radius: 0 30px 30px 0;
        animation: rectangle2Run 5s ease infinite;
    }

    @keyframes rectangle1Run {
        100% {
            width: 94%;
        }
    }

    @keyframes rectangle2Run {
        100% {
            width: 60px;
        }
    }
</style>

<body>
<div class="wrap">
    <div id="rectangle1"></div>
    <div id="rectangle2"></div>
</div>
</body>

</html>